Generally, human beings do not speak and listen at the same time. This is especially true for humans engaged in a two-way voice conversation over a telephone. Historically, this was often problematic for wireless communication devices that employed a rechargeable battery as a power source. Particularly, the transmitter and the receiver of a user's device remained on throughout a two-way voice conversation. Thus, both would draw power from the battery even though a user would either speak (i.e., transmit) or listen (i.e., receive). The increased power draw required users to recharge their batteries more often thereby decreasing talk time. In addition, keeping the transmitter on during the voice call sometimes undesirably interfered with nearby receivers.
To address these types of situations, the 3rd Generation Partnership Project (3GPP) introduced sets of specifications defining a feature called Discontinuous Transmission (DTX) mode. Generally, with DTX mode, a wireless communication device turns it's transmitter off when the user does not speak into the microphone during an active voice call. Turning the transmitter off saves battery power and reduces the undesirable effects of transmitter interference. The DTX mode is well-known, and defined for both full rate speech channels and for enhanced full rate speech channels. For full-rate speech channels, the DTX mode is defined in 3GPP TS 46.031 (V6.0.0) entitled “Discontinuous Transmission (DTX) for full rate speech traffic channels (Release 6),” and dated December 2004. For enhanced full-rate speech channels, the DTX mode is defined in 3GPP TS 46.081 (V6.0.0) entitled “Discontinuous Transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels (Release 6),” and dated December 2004.
The 3GPP also defined a similar feature to control the receiver. Specifically, the Discontinuous Receiver (DRX) feature turns off a device's receiver while the device is in an idle mode. While idle, the receiver is turned on only during predetermined time slots to allow it to listen to a paging channel. If the device receives a page, the receiver is turned on to receive voice and data over a traffic channel; otherwise, the receiver is once again turned off to conserve power resources. The DRX mode is defined in 3GPP TS 43.013 (V6.0.0) entitled “Discontinuous Reception (DRX) in the GSM system; (Release 6),” and dated December 2005.
The DTX mode saves power because it turns the transmitter off when a user is listening. Similarly, the DRX mode saves power because it turns off the receiver when the device is in an idle mode. However, once the user engages in a two-way conversation, the receiver remains turned on even when the user is speaking. There are no analogous power savings while the user is engaged in an active call.